The invention relates to a power plant utilizing wood chips as the fuel and more particularly to a fuel metering bin level control.
When operating a power plant fueled by wood chips, the wood chips are brought in by the truck load, dumped on a conveyer, which carries them to a disc screen that removes oversize chips. The oversize chips are routed to a hammer mill wherein the size is reduced sufficiently to be combined with the chips that passed through the disc screen. These chips are transported by a conveyor to a metering bin. From the metering bin the chips are fed at a controlled rate to a stoker and fire a boiler to produce steam to operate a turbine generator set to make electricity. When the metering bin is full, an augur moves the excess wood chips to another conveyor, which delivers them to a silo for storage. The stored chips are used to maintain the fuel supply when new chips are not being trucked into the plant. One of the problems is that filling the metering bin results in the chips becoming packed therein to such an extent that they bridge over the metering bin creating a void as chips are fed from the bottom of the bin into the boiler. The bridging eventually cuts off the fuel to the boiler. The only successful way to cure the bridging was to regularly allow the metering bin to empty, by shutting down the conveyor from the fuel yard. This slowed down the truck unloading operation, substantially increasing the time required to unload the daily quota of trucks.